1. Field of the Invention
The present invention relates to an inspection device and method, and particularly to a device and method for inspecting photomasks and products fabricated using the same.
2. Description of the Related Art
As part of the advancing miniaturization of large-scale integrated circuits (LSI), recently the degree of precision is increasing not only for patterned wafers, but also for the photomasks such as reticles that are used when manufacturing LSI chips. This leads to a demand for a more sensitive inspection device that can detect smaller defects on a photomask or fabricated wafer.
FIG. 12 is a block diagram that shows a conventional inspection device. The inspection device 100 compares the actual pattern of, for example, a photomask 110 with its source design data that was used when drawing the actual pattern (the process known as die-to-database inspection). In this case, the inspection device 100 is formed from the following elements: (a) a reference data generator 101 that, based on design data, generates reference data that is to be used for the inspection; (b) an inspection condition setter 102 for setting inspection conditions; (c) an image acquiring unit 103 for acquiring as image data the actual pattern of the photomask 110 that is to be inspected; (d) image converters 104 and 105 for converting the reference data and the acquired pattern data into images for the purpose of comparison; (e) a comparator 106 for comparing the reference data with the data to be inspected and detecting defects; (f) a defect memory 107 for recording the detected defects; and (g) an inspection/drive controller 108 for driving a stage 108a on which the photomask 110 is mounted as the subject of the inspection, and for controlling the entire inspection device 100.
The inspection device 100 operates as follows. When design data is supplied, the reference data generator 101 produces reference data that is in a format suitable for inspection. Then, inspection begins after the inspection condition setter 102 inputs such settings as inspection sensitivity. First, the reference data is converted into an image by the image converter 104 and input to the comparator 106. At the same time, the actual pattern of the photomask 110, which has been acquired by the image acquiring unit 103, is sent to the image converter 105 as the data to be inspected, where it is converted into an image and input to the comparator 106. The comparator 106 refers to the inspection sensitivity that was set by the inspection condition setter 102, compares the two images, and determines whether there are any defects in the photomask image. Next, in the case that defects are detected, they are recorded in the defect memory 107. The inspection/drive controller 108 inspects the entire area of the photomask 110 by scanning the stage 108a. In this way, the conventional inspection device 100 compares the actual pattern data with the reference data and detects differences as defects.
However, the conventional inspection device 100 has a problem in that when sensitivity is raised, it mistakenly generates a false defect even if that location is not a defect. Also, depending on the location of the photomask defect, some defects do not affect performance or characteristics of the products fabricated with the photomask. Such labor as the repair of defects that are not problematic is in itself a problem.